Variable-Reluctance Sensor Interface with Differential Input and Adaptive Peak Threshold

Industry's First Single-Chip Solution for Variable-Reluctance Sensor Interface and Adaptive Peak Threshold

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The MAX9924–MAX9927 variable reluctance (VR or magnetic coil) sensor interface devices are ideal for position and speed sensing for automotive crankshafts, camshafts, transmission shafts, etc. These devices integrate a precision amplifier and comparator with selectable adaptive peak threshold and zero-crossing circuit blocks that generate robust output pulses even in the presence of substantial system noise or extremely weak VR signals.

The MAX9926/MAX9927 are dual versions of the MAX9924/MAX9925, respectively. The MAX9924/MAX9926 combine matched resistors with a CMOS input precision operational amplifier to give high CMRR over a wide range of input frequencies and temperatures. The MAX9924/MAX9926 differential amplifiers provide a fixed gain of 1V/V. The MAX9925/MAX9927 make all three terminals of the internal operational amplifier available, allowing greater flexibility for gain. The MAX9926 also provides a direction output that is useful for quadrature-connected VR sensors that are used in certain high-performance engines. These devices interface with both new-generation differential VR sensors as well as legacy single-ended VR sensors.

The MAX9924/MAX9925 are available in the 10-pin µMAX® package, while the MAX9926/MAX9927 are available in the 16-pin QSOP package. All devices are specified over the -40°C to +125°C automotive temperature range.
MAX9924, MAX9925, MAX9926, MAX9927: Simplified Block Diagram MAX9924, MAX9925, MAX9926, MAX9927: Simplified Block Diagram Enlarge+

Key Features

  • Differential Input Stage Provides Enhanced Noise Immunity
  • Precision Amplifier and Comparator Allows Small-Signal Detection
  • User-Enabled Internal Adaptive Peak Threshold or Flexible External Threshold
  • Zero-Crossing Detection Provides Accurate Phase Information


  • Camshaft VRS Interfaces
  • Crankshaft VRS Interfaces
  • Vehicle Speed VRS Interfaces

See parametric specs for Sensor Interface Devices (10)

Part NumberSensor Interface TypeChannelsVSUPPLY
Low Power ShutdownOper. Temp.
minmaxtypSee Notes
MAX9924 Variable Reluctance14.55.52600No-40 to +125
$2.70 @1k
MAX9925 12600
$1.27 @1k
MAX9926 24700
$3.59 @1k
MAX9927 24700
$2.37 @1k

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX9924UEVKIT: Evaluation Kit for the MAX9924U and MAX9925
MAX9926UEVKIT: Evaluation Kit for the MAX9926U

Technical Documents

Tutorial 4697 Overview of Industrial Motor Control Systems

Tools & Models

  • MAX9924 PSPICE Macromodel
  • Product Reliability Reports: MAX9924.pdf 
    Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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